Abstract: Various embodiments are described herein relating to a radar system and associated methods for detecting targets in the presence of certain types of clutter. The radar system generally comprises hardware operatively configured to obtain first and second sets of radar return signals concurrently, first circuitry operatively configured to detect targets in the first and second sets of radar return signals, and second circuitry operatively configured to identify detected targets due to clutter.

Abstract: A bistatic radar system having a transmitter that generates unique signals at spatially independent transmitter degrees of freedom and a receiver that filters the signal at each receiver degree of freedom into a group of signals identical in number to the number of transmitter degrees of freedom. The receiver formats the filtered signals into a 2-dimensional array of elements. The receiver rotates the array so that the new axes are aligned with the Doppler gradient. The data is then re-sampled and projected to linearize the clutter signal. The receiver may be integrated with a broad class of adaptive and non-adaptive clutter mitigation approaches such as electronic clutter tuning and projected bistatic space-time adaptive processing, or STAP.

Abstract: A radar transmitter is at a first location on a moving platform and illuminates a target with a sequence of frequency modulated radar pulses. The frequency modulated pulses are linear frequency modulated, i.e. chirped. The target reflects the frequency modulated radar pulses. A receiving antenna has a difference pattern null and receives the reflections from the target as a main scatterer and an ambiguity of the main scatterer. The sequence of pulses change the start of their frequency modulation (chirp) over a SAR array. The change in start frequency from pulse to pulse allows to shift the range ambiguity so as to align with the delay/Doppler difference pattern null of the antenna. Thus, both the main scatterer as well as the shifted range ambiguity are on the difference pattern null, facilitating their cancellation.

Abstract: The invention relates to a process for the evaluating a received signal of an SAR/MTI pulsed radar system that transmits SAR and MTI pulses with respective definable pulse repetition frequency PRF_SAR and PRF_MTI, such that the received signal is a superimposition consisting of echo pulse sequences of SAR and MTI echo pulse signals. According to the invention, in the received echo pulse sequence of the received signal, each SAR echo from an area of interest is evaluated SAR process. The remaining pulses of the received echo pulse sequence of the received signal are evaluated in using an MTI process.

Abstract: A system and method is presented for detecting and classifying slow-moving and hovering helicopters from a missile's took-down Doppler radar that is compatible with the existing base of Doppler radars. This approach uses definable attributes of a helicopter rotor assembly and its extended Doppler rotor return to differentiate “rotor samples” from other samples (steps 123, 125), extract features such as bandwidth, activity, angle, and shape from the rotor samples (step 127), and classify a potential target as a helicopter or other based on the extracted rotor features and the known attributes of the helicopter rotor assembly (step 129). A target report including a classification target, range, range-rate, and angle of the extended rotor return is suitably passed to a tracking processor (step 121).

Abstract: Lower resolution and clutter-prone two-tone CW radars can have the displayed images dramatically improved by three techniques involved in the subject invention. The three techniques involved are the stepping of each of the multiple radars for readings at multiple frequencies, weighting the results to compensate for wall-induced distortions and differential image processing. In one embodiment, weights for each frequency counteract the distortion produced by particular wall. For differential image processing, temporal snapshots of the images are subtracted one from the other such that the result is only due to moving objects, thus to provide a dramatic display of the presence and position of moving individuals behind a wall.

Abstract: A linear FM pulse radar with Doppler processing of co-polarized and cross-polarized radar return signals isolates the target echo signal content associated with a moving pedestrian to provide high quality target echo data for standoff HCE detection based on polarimetric signature analysis. Baseband co-polarized and cross-polarized radar return signals are repeatedly and coherently integrated across numerous successive radar return pulses to create co-polarized and cross-polarized range vs. velocity (Doppler) data maps. The co-polarized data map is used to identify a moving pedestrian, and co-polarized and cross-polarized data subsets corresponding to the identified pedestrian are extracted and subjected to polarization signature analysis to determine if the pedestrian is bearing explosive devices.

Abstract: An apparatus for detecting clutter blocks and an interference source for dynamically establishing a clutter map includes a clutter block detecting module accumulates a plurality of range cell data of each detecting area, and compares the accumulated value with a clutter block level to define the position of a clutter block; a interference source detecting module accumulates all range cell data in each radar beam area, and compares the accumulated value with an interference source reference level to detect whether any interference source exists; and a clutter map establishing module saves the clutter maps on different beam areas in three memory blocks. When one clutter map cell is extracted, the clutter map cells on different beam areas neighboring with the beam area saving extracted clutter map cell are also extracted. The largest value among the extracted clutter map cells is being a clutter threshold value of a detected target.

Abstract: A method of detecting radar returns and measuring their parameters with or without clutter present and no clutter cancellation employed which includes transmitting at least one pulse; processing the returns surpassing a threshold detected in one range azimuth bin and by processing and separating out the returns based on their different range and azimuth. Another method includes transmission of many pulses and has minimum of one channel return surpassing detected threshold, which is detected in one range Doppler bin. The method also includes processing and thereby separating out the returns based on their different radial velocity and or azimuth and comparing the returns to a database of expected returns and adaptively processing returns that do not correspond to the expected returns. The method identifies the non-corresponding returns as indicative of at least one of clutter, land sea interface, clutter discretes and antenna sidelobe returns each without utilizing clutter cancellation.

Abstract: The invention is process for tracking a moving targeted vehicle from a remote sensor platform comprising the steps of 1) tracking the targeted vehicle and periodically recording its radar signature until its identity becomes ambiguous, 2) tracking the target after it has left its ambiguous state and periodically recording its radar signature; and 3) comparing the recorded radar signatures prior to the targeted vehicle becoming ambiguous to the recorded radar signature taken after the targeted vehicle has left its ambiguous state and determining that the targeted vehicle now tracked is the same as the targeted vehicle being tracked prior to becoming ambiguous.

Abstract: A method for discriminating and tracking a target in a clutter cloud includes transmitting a radar signal at a signal bandwidth to: identify a range extent of a clutter cloud; determine a centroid and a velocity growth rate of the clutter cloud; and identify a direction of movement of the centroid of the clutter cloud. The method may also include locking a another radar signal having a greater signal bandwidth onto the centroid of the clutter cloud whereby the centroid is tracked within one radar range resolution bin; providing a delay line that includes at least two Doppler filters and is configured to cover a Doppler frequency range corresponding to a velocity growth rate of the clutter cloud; and processing a reflected radar signal corresponding to the greater signal bandwidth. The processing of the reflected radar signal may comprise passing the reflected radar signal through the delay line to mitigate a portion of the reflected signal that is reflected by the clutter cloud.

Abstract: An anti-personnel airborne radar application for ultra slow target tracking is provided. The anti-personnel airborne radar application includes a rotorcraft and a signal processing system. The signal processing system includes a radar antenna supported by said rotorcraft, a plurality of phase centers, a conditioning circuit for each phase center, an adaptive signal processor, and an ultra slow target indicator. Each phase center is for receiving reflected radar signals received by the radar antenna. The adaptive signal processor processes the received condition signal from each of the phase centers, allowing the ultra slow target indicator to render tracking reports. A method of detecting human motion over a ground swath is also provided.

Abstract: The dual synthetic aperture array system processes returns from the receiving arrays. The two identical receiving arrays employing displaced phase center antenna techniques subtract the corresponding spectrally processed data to cancel clutter. It is further processed that a moving target is detected and its velocity, angular position and range is measured, in or out of the presence of clutter. There are many techniques presented in the disclosure. These techniques are basically independent but are related based on common set of fundamental set of mathematical equations, understanding of radar principles and the implementations involved. These many techniques may be employed singly and/or in combination depending on the application and accuracy required.

Abstract: A target is detected under a forest canopy or other elevated clutter where the target is obscured by the elevated clutter. Radar returns reflected from the target on the surface, combined with those from the elevated clutter are digitized. Motion compensation is performed for the radar returns with respect to the target to obtain a focused first synthetic aperture image of the target. Next, the radar returns are motion compensated with respect to the elevated clutter at various heights above the surface to obtain images of the elevated clutter. The elevated clutter within the images at the various heights above the surface is identified and coherently subtracted from the original synthetic aperture images.

Abstract: The subject process accepts the data from a kinematic tracker and maps them to fuzzy set conditions. Then using a multitude of defined membership functions and fuzzy logic gates, generates sensor mode control rules. It does this for every track and each sensor. The Rule with the best score becomes a sensor cue, which is used to place the sensor into one of three operating modes. If there are ambiguities do to one or more vehicles coming in to close proximity to each other process compares radar profiles of vehicle to those stored in an “on the fly” data base to eliminate the ambiguities.

Abstract: Methods, apparatus, and computer program products are provided for tracking at least one moving target with a radar device without requiring the use of Doppler information. The invention comprises scanning an area with radar signals at a first time to receive a first plurality of target data signals indicative of a position of the target at the first time and determining the position of the target at the first time by collecting the first plurality of target data signals into a first target data grouping, such that the first target data grouping defines a first reference point. Similarly, a second reference point for the target is determined for a second time, and the position of the first reference point is compared to the position of the second reference point to track the moving target. Advantageously, the tracked positions of the moving target may be used to predict a future position of the target at a subsequent time.

Abstract: A radar transmits electromagnetic energy in pulse repetition intervals and receives reflections from objects in range gates including Doppler filters. The radar approves desirable ambiguous echoes and suppresses ambiguous echoes of no interest or that interfere with the radar's display. The radar frequency varies according to a staggered or wobbling pattern. The ambiguous echoes produce one pulse in the range gates within a predetermined number of periods. The Doppler filter works with an impulse function response that includes a small number of samples. The Doppler filter, during the predetermined number of periods, gives rise to independent samples from reflectors within the radar's unambiguous range. When the independent samples exceed the small number of samples, the radar approves the ambiguous echo. Otherwise, it is suppressed. In this way, ambiguous echoes are prevented from interfering with the reception or display of echoes. The suppression of asynchronous interferences can be made easier.

Abstract: Systems and methods of tracking a beam-aspect target are provided. In embodiments, a target is tracked with a Kalman filter while detections are received. After a detection is missed, the Kalman filter may be concurrently propagated with a blind-zone particle filter until a probability that the target is in a blind zone exceeds a threshold. When the probability exceeds the threshold, the Kalman filter may refrain from further propagating. After a gated detection is received, the blind-zone particle filter and an unrestricted-zone particle filter may be concurrently propagated while a probability that the target is in an unrestricted zone exceeds a threshold. The system may return to tracking with the Kalman filter when a covariance of the unrestricted-zone particle filter falls below a predetermined covariance.

Abstract: A method according to an aspect of the invention is for filtering coherent multipulse radar, sonar or lidar returns. The method comprises the steps of separating the returns into mutually orthogonal I & Q components, performing wavelet processing on the I and Q components to generate an I & Q wavelet filter output. The I & Q wavelet filter outputs are data compressed to remove clutter portions. Data compression may be removal of large-amplitude or earliest wavelet responses. An inverse wavelet filtering function is performed on the compressed wavelet filter outputs, to thereby generate edited coherent I & Q components. Doppler filtering, is performed on the edited coherent I and Q components to thereby generate frequency-domain target data in which the minimum discernible target velocity is improved.

Abstract: A bistatic radar system having a transmitter that generates unique signals at spatially independent transmitter degrees of freedom and a receiver that filters the signal at each receiver degree of freedom into a group of signals identical in number to the number of transmitter degrees of freedom. The receiver formats the filtered signals into a 2-dimensional array of elements. The receiver rotates the array so that the new axes are aligned with the Doppler gradient. The data is then re-sampled and projected to linearize the clutter signal. The receiver may be integrated with a broad class of adaptive and non-adaptive clutter mitigation approaches such as electronic clutter tuning and projected bistatic space-time adaptive processing, or STAP.

Abstract: Radar systems use time delay measurements between a transmitted signal and its echo to calculate range to a target. Ranges that change with time cause a Doppler offset in phase and frequency of the echo. Consequently, the closing velocity between target and radar can be measured by measuring the Doppler offset of the echo. The closing velocity is also known as radial velocity, or line-of-sight velocity. Doppler frequency is measured in a pulse-Doppler radar as a linear phase shift over a set of radar pulses during some Coherent Processing Interval (CPI). An Interferometric Moving Target Indicator (MTI) radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity of a target.

Abstract: A method of removing returns from rain in Doppler radar systems (and corresponding apparatus and computer software) comprising receiving a Doppler radar return signal, transforming the signal into a range versus frequency map, for a plurality of range cells, performing a fit over frequency, for the plurality of range cells, calculating a total energy, for the plurality of range cells, comparing the calculated total energy to a threshold value, and replacing the return signal for a range cell with another signal if for the plurality of range cells the comparing step is positive.

Abstract: A radar suppresses a dc component so as to improve the precision in processing a signal that belongs to a low-frequency band. The radar comprises a mixer that mixes a transmitted signal and a received signal, and an A/D converter that analog-to-digital converts an output signal of the mixer. The radar further includes: a removing unit that removes a dc voltage component by subtracting a predetermined removal voltage value from output data of the A/D converter; and an analyzing unit that Fourier-transforms data, which has the dc voltage component removed therefrom by the removing unit, so as to analyze the data.

Abstract: The invention concerns a passive radar receiver for a received orthogonal frequency division multiplex-type signal consisting of symbol frames each emitted on coded orthogonal carriers. After formatting the received signals into digital symbols (S1 S1), a filtering circuit (2) eliminates by subtraction or using a covariance matrix, in the symbol signal at least unwanted signals with null Doppler effect so as to apply a filtered signal (X?) including essentially signals backscattered by mobile targets to a Doppler-distance correlator (4).

Abstract: An asynchronous pulse detector including a data estimator which estimates the return signal based on the corrected return signal, a detector for detecting an asynchronous pulse in the return signal, and a selector for selectively outputting the estimated return signal in place of the return signal as the corrected return signal in the event the detector detects an asynchronous pulse in the return signal.

Abstract: An embedded multi-functional preprocessing input data buffer comprises a clutter lock loop circuit, a multiplier, a mode selective multiplexer, a dual-port memory, an input multiplexer, self-testing circuit, decode circuit and an output multiplexer. The clutter lock loop and multiplication circuit selectively executes a coefficient multiplication or a clutter lock loop operation for the received data according to a working mode of the radar system. After receiving the data, the mode selective multiplexer may selectively output data processed by the clutter lock loop and multiplication circuit. The dual-port memory is coupled to the mode selective multiplexer for receiving and temporarily registering the data processed. The output multiplexer selectively outputs the data temporarily stored in the dual-port memory via a number of the output channels according to the working mode of the radar system.

Abstract: A method and apparatus for processing of a signal in which a variation in phase between a transmitted and reflected pulse is modeled, as is the amplitude of the pulse. The modeled phase and amplitude are used to smooth the data by reducing phase noise present on the signal thereby enhancing the signal to noise ratio.

Abstract: A method for automatic association of moving target indications from at least one entity traveling along a route. A moving target indicator radar is used to detect a plurality of moving target indication data. The moving target indication data proximate to the identified route is selected and presented in a distance-time graph, such that each selected moving target indication data has a unique distance along route and a unique observation-time value. The selected moving target indication data are then transformed from the distance-time coordinate to a slope-intercept coordinate, such that co-linear moving target indication data in the distance-time coordinate are transformed into a plurality of points superposed together with nearly identical slope values and nearly identical distance intercept value. The superposed points are mapped back to the distance-time coordinate, and the moving target indication data corresponding to the superposed points are thus associated.

Abstract: A method for discriminating and tracking a target in a clutter cloud includes transmitting a radar signal at a signal bandwidth to: identify a range extent of a clutter cloud; determine a centroid and a velocity growth rate of the clutter cloud; and identify a direction of movement of the centroid of the clutter cloud. The method may also include locking a another radar signal having a greater signal bandwidth onto the centroid of the clutter cloud whereby the centroid is tracked within one radar range resolution bin; providing a delay line that includes at least two Doppler filters and is configured to cover a Doppler frequency range corresponding to a velocity growth rate of the clutter cloud; and processing a reflected radar signal corresponding to the greater signal bandwidth. The processing of the reflected radar signal may comprise passing the reflected radar signal through the delay line to mitigate a portion of the reflected signal that is reflected by the clutter cloud.

Abstract: Movement of a GMTI radar during a coherent processing interval over which a set of radar pulses are processed may cause defocusing of a range-Doppler map in the video signal. This problem may be compensated by varying waveform or sampling parameters of each pulse to compensate for distortions caused by variations in viewing angles from the radar to the target.

Abstract: A method for reducing the false alarm rate, i.e. the number of alarms of fixed targets erroneously declared as moving targets in the radar images of two- or multi-channel MTI radar devices, wherein the suppression of fixed target echoes over the moving target echoes within the main antenna lobe occurs through a space time adaptive processing—STAP—filter. The method uses a comparison of the amplitude amounts or power values of the range Doppler frequency cells with a threshold that can be specified in constant terms and summary of the resulting alarms. A target function is compared with defined test functions and selection criteria are determined from suitable combined calculation methods that are applied to the test and target functions for the purpose of classifying a respective target alarm as a moving or fixed target alarm.

Abstract: A method, apparatus, and system for automatic detection of targets from radar data are disclosed. Ground moving target indicator radar is used to collect radar data which is then filtered to suppress intensity of the clutter ridge. For each working point in a set of radar data, a working first-sense circular transmit/first-sense circular receive radar cross section, a working first-sense circular transmit/second-sense circular receive radar cross section, and a working asymmetry angle are calculated from a scattering matrix, then analyzed to classify the working point as a target point or a clutter point. This analysis suitably is performed by comparing data calculated for each working point to basis data collected in a look-up table in which combinations of a first-sense circular transmit/first-sense circular receive radar cross section, a first-sense circular transmit/second-sense circular receive radar cross section, and an asymmetry angle have been classified as target points or clutter points.

Abstract: A radar surveillance system includes a plurality of satellites a plurality of medium earth orbit satellites to provide continuous, long dwell coverage of a region of interest. Each satellite has an antenna having a main reflector and a subreflector electromagnetically coupled to the main reflector. A phased array generates multiple electromagnetic beams positioned so the electromagnetic beams reflect from the subreflector onto said main reflector. The system may be used in determining slow moving targets using a combination of monopulse anomaly and target spectral width measurements. The system also performs synthetic aperture radar imagery and focussed area fast moving target detection using alternating slope linear frequency modulated pulses. The plurality of medium Earth orbit satellites include a self-contained communications system consisting of high bandwidth self-relay crosslinks, high bandwidth downlink, and direct broadcast downlinks for processed data.

Abstract: A system and method for controlling clutter Doppler spread in a bistatic radar system is developed resulting in enhanced detection of low-Doppler targets or improved SAR mode performance. In an illustrative embodiment, a bistatic radar system (10) includes a transmitter (12) for transmitting electromagnetic energy (106) towards a target (16), a receiver (14) adapted to receive the electromagnetic energy (116) reflected from the target (16), and a processor (122) for optimizing a parameter or parameters of the system such that the directional derivative of the bistatic Doppler field along the isorange contour is near a desired value. The parameters to be optimized may include the transmitter velocity vector, the receiver velocity vector, or the receiver azimuth flight direction. The desired value is the minimal absolute value of the directional derivative in order to minimize the clutter Doppler spread, or the maximum absolute value of the directional derivative in order to maximize the clutter Doppler spread.

Abstract: A method and apparatus for processing of a signal in which a variation in phase between a transmitted and reflected pulse is modelled, as is the amplitude of the pulse. The modelled phase and amplitude are used to smooth the data by reducing phase noise present on the signal thereby enhancing the signal to noise ratio.

Abstract: The present invention is a system and method for radar detection of moving targets. The radar system of the present invention has only a single transmit phase center and a single receive phase center. The method of the present invention includes radiating a set of pulses to illuminate a desired scene. The pulses are reflected off of a target and a set of return signals are received. The pulse returns are then digitized, resulting in a set of data returns. Motion compensation is then performed on the entire set of data returns. A plurality of blocks of the motion compensated data are selected that are highly overlapping in time. A plurality of images is then generated from the plurality of blocks of motion compensated data. A consecutive set of the plurality of images is then selected. Lastly, moving objects represented within the consecutive set of images are identified.

Abstract: The present invention includes a system and method for accurately locating moving targets. The system includes a targeting aircraft that has a radar system with a simultaneous SAR radar/moving target mode that generates an image and identifies moving targets in the generated image. The targeting aircraft also includes a mapping component that matches the generated image to a stored digital map, and generates moving target location information based on the matched image and map and the identified moving targets.

Abstract: A cellular radar system is disclosed for detecting and tracking objects in a surveillance area that is divided into cells. Each cell is scanned by at least two radars to produce two (or more) respective datastreams for the cell. Orbiting unmanned air vehicles can be used as radar platforms. The resulting datastreams for each cell are then multilaterated by a processor to produce a multilaterated datastream for each cell. The multilaterated datastreams for all cells are then combined by the processor and the resulting data used to detect or track one or more objects in the surveillance area. The fused multilaterated datastreams allow objects to be tracked as they move from cell to cell.

Abstract: In a process for computing the radar signals present at the output of two subapertures of an antenna of a two-channel radar system, the two subaperture channels are combined by means of a wave guide part to a sum and difference channel, and the signals of the sum and difference channel are used to compute the radar signals at the subaperture channels.

Abstract: A method (100) for coherent change subtraction of mission and reference synthetic aperture radar (SAR) data (20′,20″) is provided. The method (100) forms (102) mission and reference images (22′,22″) from the mission and reference SAR data (20′,20″), registers (122) the mission and reference images (22′,22″) on a common plane to form registered mission and reference images (24′,24″), and forms (124) the registered mission and reference images (24′,24″) into at least one patch (26) containing mission and reference data (28′,28″). The method (100) then processes (126) each patch (26) by removing (130) linear phase terms (34) from the mission data (28′), trimming (142) non-overlapping spectra of the mission and reference data (28′,28″), and balancing (144) phases and amplitudes of the mission data (28′).

Abstract: A method for reducing the false alarm rate, i.e. the number of alarms of fixed targets erroneously declared as moving targets in the radar images of two- or multi-channel MTI radar devices, wherein the suppression of fixed target echoes over the moving target echoes within the main antenna lobe occurs through a space time adaptive processing—STAP—filter. The method uses a comparison of the amplitude amounts or power values of the range Doppler frequency cells with a threshold that can be specified in constant terms and summary of the resulting alarms. A target function is compared with defined test functions and selection criteria are determined from suitable combined calculation methods that are applied to the test and target functions for the purpose of classifying a respective target alarm as a moving or fixed target alarm.

Abstract: The dual synthetic aperture array system processes returns from the receiving arrays. The two identical receiving arrays employing displaced phase center antenna techniques subtract the corresponding spectrally processed data to cancel clutter. It is further processed that a moving target is detected and its velocity, angular position and range is measured, in or out of the presence of clutter. There are many techniques presented in the disclosure. These techniques are basically independent but are related based on common set of fundamental set of mathematical equations, understanding of radar principles and the implementations involved. These many techniques may be employed singly and/or in combination depending on the application and accuracy required.

Abstract: A system and method for detecting a target. The inventive method includes the steps of receiving a complex return signal of an electromagnetic pulse having a real and an imaginary component; extracting from the imaginary component information representative of the phase component of the return signal; and utilizing the phase component to detect the target. Specifically, the phase components are those found from the complex range-Doppler map. More specific embodiments further include the steps of determining a power spectral density of the phase component of the return signal; performing a cross-correlation of power spectral density of the phase component of the return signal between different antenna-subarray (quadrant channels); and averaging the cross-correlated power spectral density of the low frequency components. In an alternative embodiment, the cross-correlation is performed on the phase component of the range-Doppler map directly.

Abstract: A method of recognising a radar target comprises producing a sequence of Doppler spectra of radar returns form a scene and producing therefrom a sequence of Doppler feature vectors for a target in the scene. Hidden Markov modelling (HMM) is then used to identify the sequence of Doppler feature vectors as indicating a member of a particular class of targets. HMM is used to identify the sequence of Doppler feature vectors by assigning to each feature vector an occurrence probability by selecting a probability distribution or state from a set thereof associated with a class of targets, multiplying the occurrence probabilities together to obtain an overall probability, repeating for other probability distributions in the set to determine a combination of probability distributions giving highest overall probability for that class of target, then repeating for at least one other class of targets and selecting the target class as being that which yields the highest overall occurrence probability.

Abstract: A bistatic radar system and method. In the illustrative embodiment, a receiver is positioned in a horizontal plane. A transmitter is then positioned in Middle Earth Orbit at a position that is nearly vertical to the plane of the receiver. This configuration provides significant flexibility for the radar system. As such, the radar system may engage in flight patterns, in which the transmitter and receiver have velocity vectors in opposite directions (GMTI mode), the same direction (SAR mode) and variations in between (mixed mode). Lastly, a broad beam is generated from the transmitter and illuminates an area enabling several receivers to simultaneously observe the illuminated area.

Abstract: A radar surveillance system includes a plurality of satellites a plurality of medium earth orbit satellites to provide continuous, long dwell coverage of a region of interest. Each satellite has an antenna having a main reflector and a subreflector electromagnetically coupled to the main reflector. A phased array generates multiple electromagnetic beams positioned so the electromagnetic beams reflect from the subreflector onto said main reflector. The system may be used in determining slow moving targets using a combination of monopulse anomaly and target spectral width measurements. The system also performs synthetic aperture radar imagery and focussed area fast moving target detection using alternating slope linear frequency modulated pulses. The plurality of medium Earth orbit satellites include a self-contained communications system consisting of high bandwidth self-relay crosslinks, high bandwidth downlink, and direct broadcast downlinks for processed data.

Abstract: A surface wave radar system including a receive antenna array (20, 22) for generating receive signals, and a data processing system (24) for processing received data representing the receive signals to mitigate ionospheric clutter. The received data is range and Doppler processed, and a spatial adaptive filter (52) is trained using training data selected from the processed data. The training data includes ionospheric clutter data and excludes cells which contain target data and substantial sea clutter. The processed data is filtered using the filter (52), which may be based on loaded sample matrix inversion. The antenna array (20,22) may be two-dimensional having an L or T shape.

Abstract: In a process for computing the radar signals present at the output of two subapertures of an antenna of a two-channel radar system, the two subaperture channels are combined by means of a wave guide part to a sum and difference channel, and the signals of the sum and difference channel are used to compute the radar signals at the subaperture channels.

Abstract: A radar system including a blanker and a sidelobe canceler is described including an open loop nulling circuit for introducing one or more nulls in the main beam and a blanker beam. With this arrangement, the blanker can be operated even in the presence of strong sidelobe jamming without the conventional problems attributable to noise amplification. Also described is an antenna configuration for implementing the open loop nulling, including a pair of orthogonal linear arrays. One of the arrays is omnidirectional in azimuth and directional in elevation and the other array is omnidirectional in elevation and directional in azimuth in order to point the main and blanker beams in the direction of jammers. In one embodiment, the radar system further includes a spoofer and the crossed linear arrays process the spoofer signals on transmit and process blanker signals on receive.

Abstract: The present invention relates to a receiving/transmitting apparatus for radiating a predetermined signal and receiving a signal arriving as a response to the radiated signal, and to a radar equipment in which the receiving/transmitting apparatus is installed. In the receiving/transmitting apparatus and the radar equipment according to the present invention, high coherency is reliably achieved without any great enlargement in hardware scale. Therefore, it is possible to realize with high reliability improvement in performance and reliability as well as price reduction, downsizing, and running cost reduction in apparatuses and systems to which the present invention is applied.